GEOCHEMICAL JOURNAL
Online ISSN : 1880-5973
Print ISSN : 0016-7002
ISSN-L : 0016-7002
Invited Reviews
Presolar silicate grains: Abundances, isotopic and elemental compositions, and the effects of secondary processing
Christine FlossPierre Haenecour
Author information
JOURNAL FREE ACCESS

2016 Volume 50 Issue 1 Pages 3-25

Details
Abstract

Close to a thousand presolar silicate grains have been identified since their initial discovery in interplanetary dust particles (IDPs) just over ten years ago. Studies have shown that silicates are the most abundant type of presolar grain other than nanodiamonds, with abundances of ~200 ppm in the most primitive meteorites and upwards of ~400 ppm in anhydrous IDPs. The oxygen isotopic compositions of presolar silicates are similar to those of presolar oxides, with the majority of the grains originating in low-mass red giant or asymptotic giant branch stars of close-to-solar metallicity. The vast majority of the grains are ferromagnesian silicates with high Fe concentrations. This, together with TEM studies indicating that many presolar silicates have amorphous structures with heterogeneous and non-stoichiometric compositions, suggests that conditions in the stellar environments in which these grains formed were variable and rapidly changing, with grain condensation under non-equilibrium kinetic conditions. Presolar silicates also reflect secondary processes taking place in the solar nebula and the parent bodies of the meteorites in which they are found. Abundance variations within individual meteorites provide constraints on secondary processes, and both thermal metamorphism and aqueous alteration result in changes to the elemental compositions of the grains. Studies of presolar silicates complement those of other presolar grain types, providing additional constraints on stellar environments and nucleosynthetic processes.

Content from these authors
© 2016 by The Geochemical Society of Japan
Previous article Next article
feedback
Top